To ETTR or not to ETTR...?

Started 3 months ago | Discussions thread
Xasan Contributing Member • Posts: 828
Thank you

bobn2 wrote:

Xasan wrote:

bobn2 wrote:

tomhongkong wrote:

Some facts

None of the below is a fact.

If I may, some of us would enjoy your answer past the headline above.

Nothing too much to take exception to - it's just that when someone declares their opinions to be facts, they set themselves a high bar.

Most people use an average auto exposure setting which is based on averaging the light measured and having an 18% greyscale exposure correct. That means that bright portion of a bright image is going to be underexposed (of course if you are using spot or centre weighted exposure that may not apply). A predominately dark image might similarly be underexposed

I think 'most people' likely use their camera's default evaluative exposure modes, which don't at all work as described.

Agree and agree.

With most digital sensors there is around one stop of 'headroom' for highlights, when the auto exposure is used. Even blinkies typically start flashing at a maximum setting of 125% so there is plenty of headroom left when they are blinking.

Depends where you're measuring headroom from. Most digital cameras don't leave a whole stop above JPEG 100%.

Agree, and depending on the tone curve applied to raw in DSP, can be less than .5 stop.

In the context of this forum particularly, many Panasonic sensored cameras have very little, or even negative headroom.

If you don't believe this, try taking a photo in RAW with 'blown' highlights and reducing the exposure in PP. You will be surprised at how much latitude is built in to your camera, which is not used when taking JPEG. Having a feeling for how much you can overexpose is a good thing.

He's talking about raw headroom, varies a lot from camera to camera.

Agree, and he's not specifying what latitude is that, part of it is because of calibration, part of it is due to channel extrapolation using AI algorithms. Quality-wise it matters.

So there is a lot of scope for 'overexposing' based on what the camera meter believes.

Getting the right exposure (and I don't mean correcting a dark image by winding up brightness with a higher iso, which does nothing for exposure) is important to improve the SNR and reduce noise, and to capture more detail in the whole image, in particular in the shadows. To be safe, and underexpose "to protect the highlights' does the reverse.

The best exposure is pretty much always the largest exposure, subject to technological and aesthetic constraints. Once you've maximised exposure the task is selecting the best ISO setting to go with it.

No doubt.

Of course if you only use JPEGs, and I accept the convenience of this strategy, you pay the price in reducing potential DR.

Not sure which is 'this strategy'. If you use OOC JPEGs, there's a lot to do with actually choosing the lowest ISO and not being lazy and letting yourself be stuck in the ISO you first thought of. Whether you think of it as maximising exposure or minimising ISO, you need to pay attention to maximising exposure.

Definitely so.

Your systematic answers are as helpful as a steady tripod. They anchor things to their proper places. Steady tripods are usually not light-weighted, too.

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